Prevention of dye-diffusion in photographic image bearing colloid layers



United States Patent 3,234,025 PREVENTION OF DYE-DIFFUSION IN PHOTO- GRAPHIC IMAGE BEARING COLLOID LAYERS Albert Emiel Van- Hoof, Berchem-A-ntwerp, and Rene Maurice Hart, Wilrijk-Antwerp, Belgium, assignors to Gevaert Photo-Producten N.V., Mortsel-Antwerp, Belgium, a Belgian company No Drawing. Filed Aug. 2, 1960, Ser. No. 46,879 Claims priority, application Belgium, Aug. 4, 1959, 581,344, Patent 39,134 2 Claims. (CI. 96-95) The present invention relates to the prevention of diffusion of dyes in colloid layers, in particular to a new process for the preparation of mordants for acid dyes and for their application, especially for the manufacture of colour images according to the hytdrotype process particularly on an improved cinematographic blank film on which colour images are printed according to the hydrotype process.

For the manufacture of colour films according to the hydrotype process, a film support bearing a relief image obtained in a photographic way is used as starting material. Said relief image consists of a colloid, in most cases gelatin. The whole is referred to as a matrix or matrix film. This matrix is immersed in a dye-solution and brought into close contact with another film which is referred to as a blank or blank film.

Because of the contact between the dyed matrix film and the blank film, the dye of the image relief of the matrix diffuses to the hydrophilic colloid layer on the blank film on which a monochrome image is formed. In the same way a second monochrome print is obtained, etc.

This dye-transfer process can thus be repeated to such an extent that many. monochrome prints can be made with one single matrix. Also multicolour images can be obtained by immersing a second matrix in another appropriate dye-solution and by transferring the dye to a blank on which already a monochrome image has previously been printed. This process can be continued with other matrices and dyes as described in Colour Cinematogra phy, A. Cornwell-Clyve, 3rd ed., 1951, pages 451-474.

Said process, however, meets with the great disadvantage that the definition of the colour image is poor, due to the lateral diffusion of the dyes in the hydrophilic colloid layer of the blank film. This lack of definition is a serious drawback when the colour image is enlarged to great dimensions e.g. during cinematographical projection on a screen.

It is already known to incorporate into the hydrophilic colloid layer of the blank film mordants which precipitate the dye so as to prevent this dye from lateral diffusion. In consequence thereof colour images are obtained showing a much better definition.

It is also known from US. specification 2,548,564 that addition polymers prepared from substituted vinyl azines and vinyl azoles containing quaternary ammonium groups can be used as mordants for soluble acid dyes in photographic layers. 7

For the same purpose it is known from the US. Patent 2,675,316 to use polyvinyl dialkylamines consisting of structural units, either quaternary or not quaternary, of the type RI/ R2 "ice wherein R and R each represents an alkyl group or together represent the atoms necessary to close an alicyclic or a heterocyclic ring.

It is further known from the Belgian specification 540,976 to incorporate polyvinyl amines into blank films as mordants for acid dyes.

Finally it is known from the British specification 830,189 to use as mordants for acid dyes hydrolyzed or solvolyzed derivatives of polymers containing structural units of the type:

wherein R represents an alkyl or aralkyl radical.

Among the many disadvantages of the mordants proposed hereinbefore, the staining, also called matrix poisoning, of the matrix by these mordants has to be mentioned. Said matrix poisoning is caused in case the used mordant is not sufficiently fast to diffusion. In consequence thereof some of these mordants pass from the blank upon the matrix when both the films are in close contact with each other. When the matrix is reimmersed into the dye solution, the latter will not only adhere on the image relief but also precipitate on those areas where the matrix has been poisoned by the mordant. Consequently, besides the desired colour image a more or less uniform colour-fog is formed on a following colour print. This harmful colour-fog formation will be repeated and evidently increased during the production of further prints. Moreover other unspecified products of the blank may cause the staining of the matrix.

Although many means are known for preventing said matrix poisoning and the subsequent formation of colour fog resulting from this staining on the prints, they are either not effective or they complicate the process e.g. by necessitating the application of special addition layers in the matrix film.

A further disadvantage of some of the used mordants resides in the fact that they result in an insufficiently low colour absorption. By colour absorption is meant the maximum colour density obtainable in definite circumstances of time and temperature under which the dyeimmersed matrix is brought into close contact with the blank. Said conditions are required by the apparatus ensuring the contact between the matrix and the blank film.

It is known from the Belgian patent specification 511,- 059 to add high molecular nitrogen bases, their salts or their quaternary derivatives, which all are fast to diffusion, as mordants to photographic and reproduction material. In said patent polyethylene imine is cited by way of eX- ample for such mordants. This polymer effects a mordant action but it has too low a color absorption and furthermore causes matrix poisoning to a very high extent.

Now it has been found that the lateral diffusion of dyes in colloid layers and the diffusion of dyes out of colloid layers can be prevented by incorporating in said colloid layers reaction products of polyethylene imine and urea.

The reaction products of polyethylene imine and urea are formed by reacting, whilst heating, a mixture which consists of polyethylene imine and urea.

Although polyethylene imine is referred to as a polymer consisting of a series of linearly bound groups, recent investigations of a commercial product have proved that polyethylene imine is composed of 307 of .CH CH NH units. 40% of 1 units. The specific viscosity of polyethylene imine meas- I ured in a 1% aqueous solution amounts to 0.22. The

ratio of the reacting amounts of polyethylene .imine and ureamay. vary within defined limits. The most suitable mordants however are obtained by condensing 0.1.to 5 7 mols urea with 1 mol polyethylene imine.

The use of an excessive amount of urea reduces, the mordant power of the polymer in such a way that the produced color image shows lack of definition. When urea is used in too small a quantity, the color absorption of the polymer is on the lower side. The structure of the polymers obtained is not exactly known, but it is admittedthat the imino groups are partially substituted by the urea.

An advantage of the mordants according to the present invention resides in the possibility that the color absorption can be brought on a favorable level by modifying the composition of these mordants,

A further important advantage of the mordants according to the present invention is the absence .of matrix staining.

Another advantage of these mordants is their applicability in colloidlayers at pH-values of about 6 to 7 without involving too high an increase of viscosity as in the case of the application of the mordant polymers previously described in the prior art.

The blank film on-which color images are printed according to the hydrotype method consists mainly of. one or more layers of a hydrophilic colloid such as gelatin,

emulsion layer.

The usual supports for the manufacture of the matrix film andthe blank film in most-cases are composed of cellulose'derivatives, especiallycellulose-esters, such as cellulose triacetate, cellulose acetobutyrate, cellulose propionate or even fully synthetic polymerization products or polycondensation products eg polyethylene glycol tere'phthalate, polycarbonates and polysulfonates.

Evidently the application of the polymers as mordants according to the present invention is not necessarily limited to the use as mordants in blanks for theproduction.

of prints according to the hydrotype process. These polymers can equally be applied to processes for the mordanting of acid dyes orof compounds with a relatively large anion, such as e.g. anti-static products, wetting-agents, etc.

One of these further ways of application is e.g.-to'use, as filter layers, layers containing a ,hydrophilic colloid such as gelatin which comprises a mordant according to the present invention and an acid dye. Such filter layers are among others employed in an antistress layer or an inter-mediate layer e.g. in a multicolor film which iscomposed of diflerent emulsion layers,- or even in an antihalo layer. The new process can. furthermore be applied in the preparation of pigmented layers suchas pigmented paper. The polymers according to the present invention can also be used in the manufacture of photographic color material for rendering colorcouplers fast to .diifusion. Detailed particulars regarding these special applica' polyvinyl alcohol, etc. coated ona film support: One ofv said composing colloid layers may be a silver. halide obtained. After decanting, the product is dissolved in: 25 cm. of distilled water, andprecipitated again in anexcess of a mixture consisting of equal parts of acetone.

and methanol. After decanting and drying, 13.8.g. of.

reaction product are obtained. Next 10 g. of this product are dissolved in 80 cm. of distilled water, neutralized with:

strong hydrochloric acid and filled up to 110 g. with water;

PREPARATION 2 i In a flask fitted with a condenser and a stirrer is brought a solution of 20.6 g. of polyethylene imine and 15 g. of urea dissolved in 220 cm. of waters This reaction mix:

ture is stirred :and refluxed for 8 hrs. at 100 C. Whereby ammonia is liberated. The polymer formed is purified by precipitation in acetone. After. decanting the polymer is. neutralized with hydrochloric acid. Finally water. is added to obtain a 10% polymer solution.

PREPARATION i 3 I Analogously to preparation 2,'20.6 g. of polyethyleneimine are .dissolvedpin 220 cm. of water and reacted. with 30 g.; of urea whilst ammonia is liberated. Then:

the polymeris purifiedand dissolved as described in preparation 2.

PREPARATION 4 500 cm. of-a 25% aqueous polyethyleneiminesolu-I tion and 25,0 cm?v of a aqueous ure-a'solution are mixed. This mixture isiboiled for 2 hrs. in an open ivessel whereby ammonia. isvliberated. The amount of evap-- orated water'is regulated by filling up with boiling water. After coolingthe reaction mixtureis purified in the same way as in preparation l by precipitationin acetone.

The following examples illustrate the invention without limiting; however, the scope thereofs Example 1 Alayer-forming solution is made of the following com-.

position:

8% aqueous gelatin solution Q 1000 10% aqueous polymer solution according to preparation 3 With hydrochloric acidN the pH is brought to 4 and a solution is added composed of Saponin g 0.5 40% aqueousformaldehyde solution. cm. 4

The resulting solution isi coated onto a support of cellulose triacetate film provided with a subbing layer, solidified and dried; on the blank film thus obtained one or more color images can be printed according to the hydrotype process. .When these images are cinematographically projected they show an enlarged image of good definition.

Example 2 A silver halide emulsion layer. used for positive prints is applied to a support of cellulose triacetate film which is provided .witha subbing layer.- Ontothis emulsion layer,

tions are disclosed in British patentspecification 830,189.

PREPARATION 1 In a flask fitted with a stirrer and a condenser 19.8 g. of a 50% aqueous polyethylene-imine solution areadded to 72 cm. ofwater and 21.6 g. of urea. The mixture obtained is refluxed for 15 hrs. whereby ammonia. is liberated. After cooling, 100 crn. of acetone are added. to the reaction mixture for precipitating the product thus a layer of following composition is coatedzl Aftensolidifying and drying, a sound .track' can photographically be applied to thefilm-thus obtained. On the; same film, three gelatin image reliefs cansuccessively be printed, each;of these reliefs having previouslybeen ima mersed intan appropriateaacid; dyestutf solution, accord.-

ing to the method disclosed ,in .Colour Cinematography) Cornwell-Clyve, 3rd edition, 1951 pages-451 -.474, in or-y der to obtain a multicolor image- Example 3 A solution A and a solution B respectively composed of:

A gelatin g 30 Ponceau 2R (Color Index No. 16,150) g 1 Water to 1000 cm.

B gelatin g 30 aqueous polymer solution (according to preparation 2) cm.

Water to 1000 cm.

are formed together at C. whilst thoroughly stirring. The resulting suspension of the insoluble complex of dyestuff and mordant polymer is coated as a light filter layer onto a support of cellulose triacetate which is provided with a subbing layer.

Example 4 tributed therein a substantially neutralized water-soluble condensation product obtained by heating in an aqueous medium a water-soluble polyethylene imine having a specific viscosity of 0.22 measured in a 1% aqueous solution and urea with the liberation of ammonia, said imine and urea being present in amounts providing a molar ratio of about 0.15:1 of urea to said imine.

2. The photographic element of claim 11 wherein said condensation product is attained by heating said aqueous medium containing said imine and urea at the boil for about 215 hours.

References Cited by the Examiner UNITED STATES PATENTS 2,912,296 11/1959 Taube et al. 260-2 X FOREIGN PATENTS 543,893 7/1957 Canada. 755,478 5/ 1956 Great Britain. 782,217 9/ 1957 Great Britain.

OTHER REFERENCES Wilfinger: Das Papier 2, pages 265- (1948).

NORMAN G. TORCHIN, Primary Examiner.

PHILIP E. MANGAN, Examiner. 

1. A PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT AND A LAYER OF GELATIN ON SAID SUPPORT, SAID LAYER HAVING DISTRIBUTED THEREIN A SUBSTANTIALLY NEUTRALIZED WATER-SOLUBLE CONDENSATION PRODUCT OBTAINED BY HEATING IN AN AQUEOUS MEDIUM A WATER-SOLUBLE POLYETHYLENE IMINE HAVING A SPECIFIC VISCOSITY OF 0.22 MEASURED IN A 1% AQUEOUS SOLUTION AND UREA WITH THE LIBERATION OF AMMONIA, SAID IMINE AND UREA BEING PRESENT IN AMOUNTS PROVIDING A MOLAR RATIO OF ABOUT 0.51:1 OF UREA TO SAID IMINE. 